ES2318961A1 - Optimized static tap changer for high-tension/medium-tension (ht/mt) and medium-tension/low-tension (mt/lt) transformers - Google Patents

Abstract

The present invention relates to a static tap changer for HT/MT and MT/LT distribution transformers based on switched thyristors, which achieves an increase in the number of output voltages of up to 50% for HT/MT transformers with linear adjustment and up to 100% for HT/MT transformers with coarse/fine regulation when the coarse winding is separated from the fine winding. In MT/LT transformers, there is an increase of 5 to 9 different output voltages using only 7 static switches, allowing, furthermore, passage from current manual regulation of output voltage to automatic or remotely controlled regulation.

Description

Static tap changer optimized for high voltage / medium voltage (AT / MT) and medium transformers voltage / low voltage (MT / BT).

Object of the invention

The present invention relates to a changer of static sockets for AT / MT distribution transformers and MT / BT based on switched thyristors that achieves an increase of the number of output voltages up to 50% for AT / MT transformers with linear regulation and up to 100% for AT / MT transformers with coarse / fine regulator when the coarse winding of the fine. In MT / BT transformers you get increasing from 5 to 9 different output voltages using only 7 static switches, also allowing the passage of the current manual regulation of the output voltage to a regulation Automatic or remote control.

Background of the invention

The maintenance of the output voltage of the distribution transformers within the allowed margins or desired depending on the circumstances of loading is coming performing traditionally by changing the relationship of transformer transformation, so that the ratio of tensions change accordingly. To do this, they endow the main windings of a set of auxiliary windings that connecting and disconnecting from the main, add or reduce you exhale, thus changing the relationship.

The switching process is performed in the Present in two basic ways: on load or without load. The Load switching is common in AT / MT transformers (High voltage / Medium voltage), whose service cannot be interrupted without seriously impair the operation of the system.

No-load switching is typical of traffic MT / BT of the Transformation Centers, in which the device switching load is too bulky and expensive, for what is allowed that your service be interrupted while performs the switching.

For load switching a regulator is used very voluminous electromechanical, with thousands elements, of slow operation and requires expensive maintenance, being also a source of numerous failures throughout life useful of the transformer by the appearance of arcs of commutation.

The tap changers in caga respond in general to three basic schemes:

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Linear regulation, in which you take them of regulation are switched successively, adding or detracting a constant number of turns according to the changer of Sockets commute one way or the other way around.

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Regulation with preselector positive-negative, in which the regulation range it is twice the tension of the regulation winding, connecting the main winding at one or the other end of the regulation and therefore, adding or subtracting the tension from it.

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Regulation with preselector coarse-fine, which allows to include or eliminate a winding without regulation jacks (coarse) whose voltage is equal to the winding with shots (fine), doubling the range of regulation of it.

For switching without load it is used in the Currently a tap changer under cover, which manually and After previously putting the transformer out of service, it allows make timely changes in the transformation relationship. In In this case, the number of possible shots and voltages is very high. scarce.

These limitations are largely solved measure in patent application P200500403, of title " Socket changer for medium / low voltage transformers ". This application presents a new approach to the application of static switches based on applicable switched thyristors almost immediately to medium / low voltage transformers with the possibility of increasing the number of output voltages of the 5 usual values up to 9 different values without it mean significant variation of the constructive disposition of the current transformer, using 8 switches static

Description of the figures

Figure one.-

Scheme of single phase coils AT / MT transformer with linear regulation. The phase consists of a main winding (P) and other regulation divided into groups of n turns between each of which there are accessible shots (t). A mobile contact (c) can move automatically or telecommanded from one to another to add or detract groups of n turns to the main winding, thus changing the transformation ratio of the transformer and with it the output voltage.

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Figure 2.-

Scheme of single phase coils AT / MT transformer with preselector positive negative. The phase consists of a main winding (P) and other regulation divided into groups of n turns between each of which there are accessible shots (t). The regulation winding joins the main one through a switch (cpn) to be able to preselect in this way the direction of the current through the regulation winding. A mobile contact (c) can scroll automatically or telecommand from one outlet to another to add or detract groups of n turns that in turn will add n or subtract n from the main winding according to the direction of the current, thus changing the relationship of transformer transformation and with it the voltage of exit.

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Figure 3.-

Scheme of single phase coils AT / MT transformer with coarse-fine preselector. The phase consists of a main winding (P), a winding of coarse regulation (B) in series with the main one, with accessible sockets (t) at its ends, and another fine regulation divided into groups of n turns between each of which there are accessible shots (t). The control winding can be attached to the coarse or to the main through a switch (cbf) to be able to preselect in this way if the coarse winding is intervened or not. A mobile contact (c) can move automatically or telecommand from one outlet to another to add or detract groups of n turns that in turn will add or subtract n from coarse winding and to the main one or only to the main winding, thus changing the transformer transformation ratio and with it the voltage output

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Figure 4.-

This figure represents the way to connect the static switches based on power electronics (I) a the regulation sockets of the existing AT / MT transformers in the actuality As indicated in the figure, they have been connected the shots that correspond to groups of turns of the winding of regulation in the sequences 1n, 3n, 3n, .., 3n, 2n in the case of be the number of groups of n turns multiple of 3 (Figure A); 1n, 1n, 3n, 3n, .., 3n, 2n in the case of the number of groups of n turns multiple of 3 plus 1 (figure B) or 1n, 3n, 3n, .., 3n, 2n, 2n in the case of being the number of groups of n turns multiple of 3 plus 2 (figure C).

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Figure 5.-

This figure represents the structure simplified of one of the medium voltage windings of a typical MT / BT distribution transformer. Each phase of the winding medium voltage is divided into separate main coils in two parts (3), (3 '), to each of which two are connected auxiliary coils (4), (5), (6), (7) by the junction points (8), (9), (10), (11), (12), (13). These terminals can turn connect or disconnect through a set of connections mechanical, (14).

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Figure 6.-

The figure represents a single phase of the medium voltage winding of a MT / BT transformer equal to represented in figure 5 using 8 static switches based on switched thyristors (16), (17), (18), (19), (20), (21), (22), (23).

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Figure 7.-

The figure represents a single phase of the medium voltage winding of a MT / BT transformer equal to represented in figure 5 using 7 static switches based on switched thyristors (16), (17), (18), (19), (20), (21), (22).

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Figure 8.-

The figure shows the scheme of a single phase of the high voltage winding of an AT / MT transformer with the structure corresponding to a linear regulation to which the electromechanical regulator has been replaced by switches static based on power electronics. The winding of regulation is divided into groups of regulation coils with the sequence of turns 1n, 3n, .., 3n, 2n, among which are n the regulating sockets to which the switches are connected static Said regulation winding is connected in series to the main winding, represented in the figure with the letter (P).

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Figure 9.-

The figure shows the scheme of a single phase of the high voltage winding of an AT / MT transformer with the structure corresponding to a regulation with preselector coarse-fine, to which the regulator has been replaced electromechanical by static switches based on electronics of power The fine regulation winding is divided into groups of regulation coils with the sequence of turns 1n, 3n, .., 3n, 2n, among which are the regulation sockets a which connect static switches based on power electronics Said fine regulation winding can be connected to coarse winding (B) in three ways different: directly in series with this one (figure I), through two static switches that allow adding or bridging (figure II), or through four static switches (figure III) that allow polarization directly or inversely before connect it or not to the main winding (P).

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Figure 10.-

The figure shows the scheme of a single phase of the high voltage winding of an AT / MT transformer with the structure corresponding to a linear regulation to which the electromechanical regulator has been replaced by switches static based on power electronics. The winding of regulation is divided into 5 groups of regulation coils with the  sequence of turns 1n, 3n, 3n, 3n, 2n, among which is n the control sockets to which the switches are connected static (10a, 10b, .., 10l). Said regulation winding is connects in series to the main winding, represented in the figure with the letter (P).

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Figure eleven.-

The figure shows the scheme of a single phase of the high voltage winding of an AT / MT transformer with the structure corresponding to a regulation with preselector coarse-fine, to which the regulator has been replaced electromechanical by static switches based on electronics of power The fine regulation winding is divided into 5 groups of regulation coils with the sequence of turns 1n, 3n, 3n, 3n, 2n, among which are the regulation sockets a which connect static switches based on power electronics (11a, 11b, .., 11l). Said winding of Fine regulation connects to coarse winding (B) through two static switches (11m, 11q) that allow adding or bypass it before connecting it to the main winding (P).

Brief Description of the Invention

The present invention consists of a changer of static sockets that allows versions applicable to both high voltage to medium voltage reducing transformers (AT / MT transformers) as to average reducing transformers Low voltage voltage (MT / BT transformers) based on power electronics with a new configuration of the elements that integrate it, so that in the case of transformers AT / MT, the direct replacement of the tap changer is achieved electromechanical by another electronic with minimization of the number of static switches used in the tap changer e even increasing the range of regulation in the types of linear regulation and preselector regulation coarse-fine, and in the case of transformers MT / BT 9 different output voltages are achieved using only 7 static switches, without implying relevant changes in the structure and configuration of the transformers usually used in current facilities.

The latter case significantly improves the 8 static switch solution proposed so far, given that reducing the number of switches is an important factor in the practical application of both technical and system economically.

Detailed description of the invention

The invention consists of a new form of regroup the regulation windings and the sockets that give access to the same, replacing the mechanical tap changers and electromechanical by others based on static switches that allow in any case the regulation in load and automated or telecommanded

Each phase of a winding with regulating sockets can be represented as indicated in figure 1. Between each two sockets there is a fixed number of turns n corresponding to a step of tensions. As the main contact goes through the shots, turns are added or subtracted in groups of n units to the main winding (P), thus making the regulation. In turn, if the direction of the current through the turns is changed, the voltage corresponding to each step may be subtracted instead of added, thus doubling the range of regulation, as indicated in Figure 2. Current mechanical systems They switch from one outlet to another by means of sequential mobile contacts that only allow slow ups or downs to scale and cause switching arcs that require permanent maintenance. The replacement of these mobile contacts by electronic power switches based on switched thyristors avoids these problems, allowing rapid jumps of any magnitude within the range of the regulator, without switching arcs.

The present invention takes advantage of that ability to electronic switches to get additional advantages without implying changes in the windings of regulation.

Thus, by changing the meaning of the current polarizing the control coils in direction conversely, you can reduce the number of shots required grouping auxiliary regulation windings, formed originally by k groups of n serial turns and intermediate shots between each of them, in sets of 1n turns, 2n turns or 3n turns connected in series in certain sequences. These clusters are optimal if they are performed in the sequences following:

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1n, 2n, for 3 groups of n you turn

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1n, 1n, 2n, for 4 groups of n you turn

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1n, 2n, 2n, for 5 groups of n you turn

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1n, 3n, 2n, for 6 groups of n you turn

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1n, 1n, 3n, 2n, for 7 groups of No turns.

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1n, 3n, 2n, 2n, for 8 groups of No turns.

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1n, 3n, 3n, 2n, for 9 groups of No turns. ...............

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That is, each phase of the winding of regulation will always have an initial group of 1n turns and another end of 2n turns. If the number k of groups of n turns is multiple of 3, the remaining turns will be grouped in (k-3) / 3 groups of 3n turns. If the number k of groups of n turns exceeds in a unit a multiple of 3, it will place a second group of 1n turns and the rest will be grouped n in (k-4) / 3 groups of 3n turns. If the number k of groups of n turns exceeds by two units a multiple of 3, it will place a penultimate group of 2n turns before the last, and the remaining will be grouped into (k-5) / 3 groups of 3n you turn

Therefore, the groupings must be made in the sequence 1n, 3n, 3n, ..., 3n, 2n , in the case of a number of groups of n turns multiple of 3, or 1n, 1n, 3n,. .., 3n, 2n; and 1n, 3n, ..., 3n, 2n, 2n for intermediate cases between said multiples.

The schemes corresponding to each of the Clusters are indicated in the three graphs in Figure 4. In they can be seen that, as they open or close the static switches, add or detract coils can be achieved in groups of n turns, within a range from zero to the total sum of turns of the regulation winding, in regular steps. In addition for each output voltage value only two of the switches have to be closed, all being other open, which implies that there will only be two switches in series simultaneously in each case. It can also be seen that they make two shots unnecessary for each group of 3n turns and one take for each group of 2n turns.

The invention can be divided into two systems basic, as applicable to AT / MT transformers or to MT / BT transformers.

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- MT / BT transformers

The present invention replaces the model of static switch sockets of 8 switches for another that performs the same function but using only 7 switches, without rather than regrouping auxiliary windings differently, as follows:

The usual simplified configuration of a MT / BT distribution transformer is indicated in figure 5. In she observes one of the three phases of the MT winding that It consists of a main coil divided into two parts (3) and (3 '), each of NP / 2 turns, to each of which two are connected auxiliary coils (4), (5), (6), (7), each of N turns. The junction points (8), (9), (10), (11), (12), (13), are accessible by terminals welded to the effect (sockets). In the configuration current these terminals can in turn be connected or disconnected by means of a set of mechanical connections, (14), which are operated manually through a mechanism whose command is located on the lid of the transformer tank, and that respond to wiring diagram of the figure. That way, closing and opening the connections, the auxiliary coils are added to the main coils, changing the transformation ratio and with it the output voltage of the transformer, achieving 5 different output voltages for the same input voltage, or either the same output voltage for 5 different values of the input voltage

In figure 6 8 switches are used (16), (17), .., (23) and 9 transformation ratios are achieved different and with it 9 different output voltages without changing the structure or number of the coils currently existing in MT / BT transformers. If it becomes necessary to separate the coils auxiliary of the main ones to adopt the configuration of the scheme, what can be done with minimal intervention in the existing transformers or immediately in those of subsequent manufacturing The increase in the number of tensions is achieved because the assembly allows current circulation both in one direction and the opposite in each auxiliary coil, depending on which switches are open or closed, so that generated flows can be added or subtracted, this being last possibility the one that allows the increase of values of voltage obtainable, as indicated in the following table:

one

In this way, the generated flow will be added or subtract the principal according to the connection, while in the current assemblies only adds up, thus being able to add four values more than 5 of the assembly of figure 5 without changes significant in the usual structure of transformers currently in use, as indicated in the previous table.

However, the present invention proposes a even more economical configuration that also gets 9 different transformation relationships and with it 9 tensions of output, but using only 7 switches instead of 8, with one simple variation of the scheme, as seen in Figure 7, and in the data in the following table:

2

As can be seen from the table and figure 7, by simultaneously activating two of the switches, get the current to take up to nine routes possible through medium voltage winding; a first route that avoids auxiliary windings, closing the switches (16) and (17), four different paths that cross auxiliary windings in a "positive" sense, closing the switch pairs each time ((16), (19)), ((16), (20)), ((18), (22)), ((16), (22)), and four routes that cross auxiliary windings in a "negative" sense, closing the switch pairs each time ((17), (21)), ((19), (21)), ((20), (21)), ((17), (18)), generating nine levels of possible voltage at the output of the transformer.

The latter case significantly improves the 8 static switch solution proposed so far, both in technical feasibility as economic, because the number of static switches is decisive, both for its cost, as for the space they occupy in the transformer and the need to control and cooling of power electronics elements employees.

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- AT / MT transformers with linear regulation

This type of load regulation uses a on-load tap switch that adds or detracts packets of n turns, to regulate the output voltage in steps same, as indicated in figure 1. Figure 8 shows a configuration proposed in this patent. Winding main is indicated by the letter P, and the socket grouping and static switch layout of the regulation winding proposed by the present invention to optimally achieve voltage regulation with a double expansion of the regulation range, by allowing polarization of the coils in both directions, analogously to the method indicated in the application to MT / BT transformers. In addition, the number of shots required in the the regulation winding.

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- AT / MT transformers with coarse / fine preselector

In this type of regulation, represented in the Figure 3, the winding with sockets is connected to the main through a switch that allows you to add a second or not auxiliary winding (coarse winding, indicated by the letter B) with only two shots and with a number of turns equal to the total of winding with shots. Figure 9 (I) shows the configuration proposed in this patent capable of performing same functions as indicated in figure 3, without making changes in the original structure of the windings, with a decrease in number of shots and preselector elimination (cbf). In figure 9 (II) the proposal is indicated in this invention that allows adding a 50% more voltage steps, by allowing to reverse the polarization of the winding with shots, grouping these according to the optimal layout already indicated. In addition, the number of shots required without changing the structure of the windings, as in the previous case. Also, if possible separate the coarse winding from the main one, they could be increased the steps up to 100%, using two more switches than also allow reverse polarization of coarse winding, as indicated in figure 9 (III).

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- AT / MT transformer with preselector positive negative

In this case, the winding with shots is connect to the main one through a switch so that the current can polarize auxiliary windings on both senses, with which the tension of each scale can be added or Subtract from that of the main winding, as indicated in Figure 2.  The configuration proposed in this patent is indicated in figure 8 for this type of regulator, in which the number of regulation sockets and the switch is removed corresponding to the positive-negative preselector (cpn).

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Embodiment of the invention - MT / BT transformers

From the scheme indicated in figure 7 corresponding to a phase of the medium voltage winding of a MT / BT transformer, and considering a voltage ratio Typical 20,000 / 400V in nominal conditions, shown then the different values of output voltages that can be obtained according to the state of the switches, assuming a fixed supply at 20,000 V.

3

As can be seen, the regulation of output voltage is much wider, allowing to adapt to a greater range of variations in the input voltage or falls of voltage, and also do it automatically without interruption of supply.

- AT / MT transformers with linear regulation or with positive-negative preselector

If we consider the scheme in Figure 8 and it Applies to a 66/20 kV transformer, whose winding of regulation has 12 steps of n turns, as indicated in the Figure 10, each of which corresponds to 1% of the tension nominal, output values from 17600 V up to 22400 V, in 200 V steps, similar to that indicated in the  previous example of the MT / BT transformer.

So, to get the relationship of tensions nominal, it will be enough to close switches 9a and 9b, keeping Open others. To add 7n turns, the 9a and 9h switches. To detract 5n turns (add 5n turns reverse polarized) switches 9k must be closed and 9h In an analogous way, we must proceed with everyone else values:

4

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- AT / MT transformer with coarse fine preselector

If the scheme in Figure 9 (II) is considered and It is applied to a 66/20 kV transformer, whose winding of "fine" regulation has 12 steps of n turns, as indicated in figure 11, each of which corresponds to 1% of the nominal voltage Un, and a regulation winding "coarse", indicated in the figure with the letter B, of 12n turns, output values from 15200 V to 22400 V could be obtained in 200 V steps, similar to the one indicated in the example front of the MT / BT transformer.

So, to get the relationship of tensions nominal, it will be enough to close switches 11a, 11b and 11m, keeping others open. To add 7n turns they will have to Close switches 11a, 11h and 11m. To detract 5n turns (add 5n reverse polarized turns) the 11k, 11h and 11m switches. To detract 15n turns they will have to close for example switches 1le, 11d and 11q. So In the same way, all other values must be followed:

5

Proceeding in the manner indicated in the table the range of stresses indicated in the example can be achieved.

Similarly, the other two would proceed possible configurations applicable to transformers with coarse-fine preselector indicated in figure 9 (I) and 9 (III).

Claims (7)

1. Tap-changer device for medium / low voltage transformers, characterized by being a main winding divided into two equal parts (3), (3 ') and a series of auxiliary windings (4), (5), (6) and (7), which incorporate into the sockets of said auxiliary regulating windings (16), (17), (18), (19), (20), (21) and (22), seven electronic switches static based on power electronics, so that six of the seven electronic switches (16), (17), (18), (19), (21) and (22) are distributed so that three of them (16) , (18) and (21) each connect one half of the main winding (3) with an intermediate socket of the auxiliary windings (8), (9) and (13), and each of the other three (17), (19) and (22) connect one of said sockets with the other half of the main winding (3 '); the seventh switch (20) is connected between the intermediate socket (10-11) and the second half of the main winding (3 '), such that by means of the simultaneous operation of two of said switches nine possible paths of the current through the medium voltage winding; a first route that avoids auxiliary windings, four different paths that cross auxiliary windings in a "positive" direction and four paths that cross auxiliary windings in a "negative" direction, generating nine possible voltage levels at the output of the transformer. 2. A tap-changer device for high / medium voltage transformers according to claim 1, characterized in that the regulating winding is formed by a number k of auxiliary coils multiple of three, capable of replacing the electromechanical regulator without altering the winding configuration. of the transformer, minimizing the number of static switches (I) and regulation sockets (t) used. 3. A tap-changer device for high / medium voltage transformers according to previous claims, characterized by using electronic switches distributed in parallel two to two on the sockets, grouping the auxiliary coils, each of n turns, in a first group of n turns, in series with (k-3) / 3 groups of 3 turns and in series with a last group of 2 turns, using only the existing regulation sockets between each of these groups, to which the static switches are connected. 4. Socket changer device for high / medium voltage transformers according to previous claims, characterized in that the regulating winding is formed by a number k of auxiliary coils multiple of three plus one, capable of replacing the electromechanical regulator without altering the configuration of the transformer windings, minimizing the number of static switches (I) and regulation sockets (t) used. 5. Socket changer device for high / medium voltage transformers that replaces the electromechanical tap changer of transformers equipped with a regulator with a coarse-fine preselector with another that uses static switches based on power electronics, according to any of the configurations described in the previous claims for the fine regulation winding characterized in that it does not alter its original structure or that of the main winding (P), does not perform regulation on the coarse winding (B), eliminating the need for the preselector (I) and allowing the same number of different voltages than the electromechanical regulator it replaces. 6. Socket changer device for high / medium voltage transformers, which replaces the electromechanical tap changer of transformers equipped with a regulator with a coarse-fine preselector with another that uses static switches based on power electronics, according to any of the configurations described in the previous claims for the fine regulation winding characterized in that it does not alter its original structure or that of the main winding (P), allowing the flow or not of the current through the coarse winding (B) by two switches, increasing the number of voltages different than 50% possible output compared to the electromechanical regulator it replaces, eliminating the need for the preselector. 7. Socket changer device for high / medium voltage transformers that replaces the electromechanical tap changer of transformers equipped with a regulator with a coarse-fine preselector with another that uses static switches based on power electronics according to any of the configurations described in the previous claims for the fine regulation winding, characterized in that without altering its original structure or that of the main winding (P) and by using 4 static switches and the physical separation of the coarse winding B from the main winding P allows the circulation of the current by the coarse winding in both directions, increasing the number of different possible output voltages by 100% with respect to the electromechanical regulator it replaces, eliminating the need for the preselector.